Get a manual, and work up to maximum loads with either the H-110, or the 296, and you'll likely have a great load giving you somewhere between 1300-1400 fps.
Another good powder to try is AA-9 (what I'm using). This powder gives good velocity/accuracy, but tends not to be quite as dirty from my experience.
I'm in the proccess of testing out some Lil' Gun in my 357 rifle right now, but haven't tried any combinations using it in my 6.5" Blackhawk yet. It's probably the best powder I've ever tried in the Rifle so far, but I still have some work to do on it, before I commit to using it.